LWG issue 1134 removed the resolution of LWG 551, leaving an incorrect specification for
the behavior of <complex.h>. This header is currently required to make std::complex (and
associated functions) visible in the global namespace, but should not be so required.

-2- Every other C header, each of which has a name of the form name.h, behaves as if each name placed
in the standard library namespace by the corresponding cname header is placed within the global namespace scope.
It is unspecified whether these names are first declared or defined within namespace scope (3.3.6) of the namespace
std and are then injected into the global namespace scope by explicit using-declarations (7.3.3).